Road planing machine

ABSTRACT

A small road planing machine for doing close work. The machine is supported on the road surface by two wheels on one side, and one wheel on the opposite side. The two wheels on the one side are power driven to propel the machine. A road planing or cutting drum is at the one side of the machine intermediate and longitudinally aligned with the two wheels. The road planing or cutting drum is transversely aligned with the one wheel on the opposite side. The road planing drum is adjustable upwardly and downwardly, and is adjustable in its inclination to meet the road surface and to cut the road surface to a preselected depth. The two wheels at the one side of the machine may be turned for steering the machine. The axes of the two wheels at the one side and the one wheel at the opposite side intersect in a point in all turned positions of the two wheels, such that the wheels travel about the point of intersection during turning. The road planing drum also travels about the point of intersection during turning of the road planing machine, which permits accurate steering of machine with the planing or cutting drum operating in a curved path.

United States Patent [1 1 Wall et al.

[ ROAD PLANING MACHINE [75] Inventors: Christopher Wall; Ronald Scaife;

Thomas A. Wood, all of Wakefield, England [73] Assignee: British Jeffrey-Diamond Limited,

Dallas, Tex.

[22] Filed: Oct. 23, 1973 [21] Appl. No.: 408,596

1 July 22, 1975 Primary Examiner-Ernest R. Purser Assistant ExaminerWil1iam F. Pate, lll Attorney, Agent, or Firm-David Young; John M. Lorenzen [5 7] ABSTRACT A small road planing machine for doing close work. The machine is supported on the road surface by two wheels on one side, and one wheel on the opposite side. The two wheels on the one side are power driven to propel the machine. A road planing or cutting drum is at the one side of the machine intermediate and longitudinally aligned with the two wheels. The road planing or cutting drum is transversely aligned with the one wheel on the opposite side. The road planing drum is adjustable upwardly and downwardly. and is adjustable in its inclination to meet the road surface and to cut the road surface to a preselected depth. The two wheels at the one side of the machine may be turned for steering the machine. The axes of the two wheels at the one side and the one wheel at the opposite side intersect in a point in all turned positions of the two wheels, such that the wheels travel about the point of intersection during turning. The road planing drum also travels about the point of intersection during turning of the road planing machine, which permits accurate steering of machine with the planing or cutting drum operating in a curved path.

20 Claims, 4 Drawing Figures SHEET PATENTED JUL 2 2 I975- SHEET mtminmz m5 ROAD PLANING MACHINE BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to road planing machines and more particularly to a small road planing machine that is capable of doing close work.

2. Description of the Prior Art The finished surfaces of roads are customarily concrete or asphalt. Such surfaces require repairs from time to time, which may initially involve repaving worn and damaged places, and ultimately requires repaving of the entire surfaces. Such repaving is most expeditiously done by applying a new layer of asphalt over the original road surface. Each time that this is done the process of repaving increases the height of the road surface and decreases the depth of the gutters at the sides. As the new road surface becomes worn and damaged, it becomes desirable at times to remove the surface material prior to resurfacing, in order to avoid further increase in the height of the road surface. Such removal of the road surface has the advantage to provide a better surface for the application of the new material which is usually asphalt.

Another undesirable road condition is that of uneven wear of the road surface resulting in depressed areas, such as in the places that are most heavily travelled by vehicles. Resurfacing of such places produces uneven compaction, and eventually the original depressions reappear. Therefore, resurfacing is not satisfactory for such areas. Resurfacing of the road surface also causes a problem around manholes and grating, for the reason that these are left below the new surface, or need to be raised to be level with the new surface. Another problem that occurs is that at corners where vehicles turn there is a mat movement or side slippage of the road surface, resulting in depressed worn areas that cannot be satisfactorily resurfaced. Still another problem condition occurs in reinstatement work, for example when a trench is dug and then refilled and resurfaced. After a time there is settlement of the material and a depressed area appears on the surface. This is not satisfactorily corrected by resurfacing because of the uneven compaction of the surface material. All the problem conditions mentioned may be corrected by removing the worn or depressed areas of the road surface and repaving such areas, rather than merely overlaying another layer of road surfacing material.

In the removal of the existing asphalt road surfaces, it has been customary to apply heat to the surface to soften the asphalt material. Then the surface material is removed by scraping it off from the underlaying material. This heating and scraping process usually involves the use of heating equipment which covers rela tively large sections of the road surface and heats the same by the application of flames to the surface, or infra-red heat, or the luminous wall method of applying heat. Such equipment is unwieldy because of its size, and the combustion requires careful guarding of the equipment. Also, the combustion produces noxious and undesirable fumes. The heating methods are unreliable because of the difficulty in controlling the penentration of the heat. A further complication is that of climate conditions, that is the inability to operate during wet weather and during extreme cold when the heat may be insufficient to heat the road surface to the required degree to soften the material, or may simply be inefficient due to the magnitude heat and fuel that is required.

It has been proposed to replace the heating and scraping process of removing road surfaces by a cold planing process. The equipment for such cold planing typically involves a rotating drum with cutting bits disposed on the circumference of such drum. The machine is propelled over the road surface with the cutting drum and its bits in engagement with the road surface, and rotated to cut into the material of the road surface to a pre-selected depth for removing the surface material from the road preparatory to applying a new layer of material and repaving the road. Such planing equipment usually has the ability to cut concrete surfaces as well as asphalt.

One form of road planing machine is illustrated in U.S. Pat. No. 3,606,468, issued Sept. 20, 1971 for Machines for Planing Road-Like Surfaces. This is a selfpropelled machine which has a planing or cutting drum that is rotated in engagement with the road surface for removing the surface material. The planing or cutting drum is of substantial width so that in each pass of the machine, a substantial area of the road surface may be cut or planed. By adjustment of the machine, the depth of cut can be controlled to a pre-selected depth. The material which is cut from the road surface may be collected by clean-up apparatus, which is incorporated in the planing machine as illustrated in U.S. Pat. No. 3,606,468, or by auxiliary equipment which follows the road planing machine,

A planing machine such as that illustrated in U.S. Pat. No. 3,606,468, is particularly constructed to work large areas of the road; therefore, it is not suited for doing close work such as in small areas, such as worn or depressed areas, and around interruptions in the paved road surface, such as man-hole covers and gratings. Such close work requires a planing machine with a substantially smaller planing drum, for example, as illustrated in U.S. Pat. No. 3,266,846, issued Aug. I6, 1966 for Surface Conditioning Machine. In this patent the planing or cutting drum is cantilevered out to one side of the machine beyond the wheels for cutting the road surface. The machine of this patent is of a substantially conventional machine frame construction with the planing or cutting drum located out to one side of the machine beyond the wheels.

SUMMARY OF THE INVENTION In accordance with this invention there is provided an improved road planing machine which is capable of doing close work to remove road surface material in small areas, such as worn or depressed areas, around man-hole covers and gratings, and similar close places. This machine has a rotating planing or cutting drum which is disposed in engagement with the road surface to cut the surface material. The planing or cutting drum is at one side of the machine intermediate fore and aft wheels by which the machine is propelled. These fore and aft wheels are also steerable to permit the making of close turns, thereby to operate the planing or cutting drum in a circle of small radius. At the opposite side of the machine there is another wheel, which is in transverse alignment with the planing or cutting drum. The cutting drum is mounted on a support which is adjustable upwardly and downwardly, and also in its inclination, by which the cutting drum position can be adjusted to meet the road surface and cut to a preselected depth.

It is a prime object of this invention to provide an improved road planing machine to work in close places.

It is another object of this invention to provide an improved road planing machine which is of small size and may be closely maneuvered in close places to remove road surface material.

It is a further object of this invention to provide an improved road planing machine with a rotating planing or cutting drum that is positioned intermediate fore and aft wheels that are steerable to closely maneuver the cutting drum.

It is still another object of this invention to provide an improved road planing machine in which the planing or cutting drum is positioned at one side of the machine intermediate fore and aft steering wheels, and there is a third ground engaging supporting wheel at the opposite side of the machine which is in transverse alignment with the cutting drum.

It is still a further object of this invention to provide an improved road planing machine in which the planing or cutting drum is disposed at one side of the machine and can be adjusted upwardly and downwardly to control the depth of cut in the road surface, and can be adjusted in its inclination to meet the road surface, in order to accurately control the cutting of the material from the road surface.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. I is a side elevational view of the road planing machine of this invention;

FIG. 2 is a plan view of the road planing machine;

FIG. 3 is a sectional view of the road planing machine taken on the line 33 in FIG. I; and

FIG. 4 is a diagrammatic illustration of the hydraulic system for the road planing machine.

DESCRIPTION OF PREFERRED EMBODIMENT Referring to the drawings, there is illustrated therein a road planing machine constructed in accordance with the invention. The machine 10 has a main frame 11, that extends in the longitudinal direction. At one side of the main frame 11 there is a fore ground engaging supporting wheel 12 and an aft ground engaging supporting wheel 13, which are disposed at about opposite ends of the main frame. At the opposite side of the main frame 11 there is ground engaging supporting wheel 14 which is located approximately mid-way of the length of the main frame 11. A guard 15 overlies the wheel I4. At the one side of the road planing machine 10, there is a planing or cutting drum 16 which is in longitudinal alignment with the fore and aft wheels 12, 13, and is disposed midway between the wheels l2, 13. The cutting drum 16, is transversely aligned with the wheel 14 on the opposite side of the machinev 10, with the axes of the wheel 14, and of the planing or cutting drum 16 lying in the same upright plane. The wheel 14 is also midway between the fore and aft wheels 12, 13 in the longitudinal direction of the main frame 11. The fore and aft wheels 12, 13 are driven wheels by .which the road planing machine 10 is propelled over the road surface. The wheels 12, 13 are also steerable for turning the road planing machine 10 to direct the cutting drum 16 in a curved path. The wheel 14 at the opposite side of the machine 10 is rotatably mounted on a fixed axle 17, which is secured to the main frame 1 1.

The fore wheel 12 is rotatably secured to a motor 20 by which the wheel is driven. Similarly the aft wheel 13 is secured to a motor 21 by which it is driven. The motors 20, 21 may be hydraulic motors which are operated by hydraulic fluid under pressure supplied from a hydraulic pump 22, that is driven by an internal combustion engine 23 mounted on the main frame 11. A charging pump 24 is associated with the pump 22 to maintain the supply of hydraulic fluid to the pump 22, as will be explained hereinafter. The pump 22 is reversible and of variable speed so as to operate the hydraulic motors 20, 21 in reverse directions and at variable speeds.

A clevis 25 extends from the motor 20 to engagement with a supporting arm 26 near the front end of the main frame 1 l. Upright pivot 27 connects the clevis 25 to the supporting arm 26 and thereby permits turning or steering movements of the fore wheel 12 about the axis of the upright pivot 27. Similarly, there is a clevis 28 which extends from the motor 21 to a supporting arm 29 near the rear end of the main frame 11. A pivot 30 connects the clevis 28 to the supporting arm 19 and permits turning or steering movement of the aft wheel 13 about the axis of the pivot 30.

The steering mechanism for the fore and aft wheels l2, 13 has a main steering link 31, which is pivotally mounted on the main frame 11 on a pivot 32. The main steering link 31 has operating arms 33, 34 which extend in opposite directions from the pivot 32. The operating arm 33 is connected to one end of a fore steering link 35 by a pivot 36, and the other end of the link 35 is connected to a steering arm 37 by a pivot 38. The steering arm 37 is secured to the clevis 25.

The steering mechanism further includes an aft steer- H ing link 39 connected at one end to the operating arm 34 by a pivot 40. The other end of the steering link 39 is connected by a pivot 41 to a steering arm 42, which is secured to the clevis 28.

The main steering link 31 is actuated by a double acting hydraulic steering cylinder 43 having its cylinder end secured to the main frame 11 by a pivot 44, and its rod end secured to the main steering link 31 by a pivot 45. The retraction and extension of the steering cylinder 43 causes the main steering link 31 to turn in the clockwise and counter-clockwise directions, respectively, thereby turning the fore and aft wheels 12, 13 in opposite directions, through the steering links 35, 39 and the steering arms 37, 42, respectively. The steering linkages are such that the wheels l2, 13 may be turned through relatively large angles, which may be of the order of to permit extremely close turns of the road planing machine 10, which is to say that the machine 10 can be turned in circles of small radius.

The steering linkages turn the fore and aft wheels 12, 13 through the same angle in opposite directions. Since the opposite wheel 14 is located midway between the fore and aft wheels l2, 13 in the longitudinal direction of the planing machine 10, whenever the fore and aft wheels 12, 13 are turned, their axes 46, 47, respectively, intersect the axis 48 of the opposite wheel 14 in a point of intersection 49. When the planing machine 10 is steered the wheels 12, l3, l4 follow arcuate paths having the point of intersection 49 as the centers of such paths. The axis of planing or cutting drum 16 is in the same upright plane as the axis of the opposite wheel 14, and therefore, when the planing machine is steered, the cutting drum 16 also moves in an arcuate path that has its centre on an upright projection of the point of intersection 49. The system as described is such as to permit accurate steering of the planing machine to direct the planing or cutting drum in a close arcuate path, and especially in arcuate paths of very small radius, as would be necessary in cutting a road surface around a man hole.

When the fore and aft wheels 12, 13 are turned in the opposite direction, their axes 46a, 4711, respectively, intersect the axis 48 of the opposite wheel 14 in a point of intersection 49a. In this condition of steering the several wheels 12, 13, 14 travel in arcuate paths about the point of intersection 49a as a center, and the planing or cutting drum 16 also follows a curved path in its opera tion about the point of intersection 49a as its center.

There is an operators station 50 near the rear of the main frame 11. The various controls for operation of the road planing machine 10 are located at the operators station and include a steering wheel 51. At the lower end of the steering wheel 51 there is a hydraulic control device 52 for controlling the supply of hydraulic fluid to the steering cylinder 43, and thereby to steer the road planing machine 10. The hydraulic fluid for operating the steering cylinder 43 is supplied by a hydraulic pump 53 driven from the engine 23 as will beexplained in greater detail hereinafter.

At the one side of the road planing machine 10, there is an upright support 55 for the cutting drum 16, the latter being rotatably mounted at the lower end of the support 55 on a shaft 56. A motor 57 is secured to the upright support 55 at the upper end thereof, and this mayconveniently be a hydraulic motor driven by hydraulic fluid under pressure supplied from the pump 54. The upright support 55 is a housing for the drive from the motor 57, to the cutting drum 16. Such drive has a drive shaft 58 extending from the motor 57 into the support 55, and spline connected to a double sprocket 59 to drive the latter. A double strand drive chain 60 is engaged with the double sprocket 59 and with a driven double sprocket 61 at the lower end of support 55 to transmit the drive to the lower driven sprocket 61, the latter being keyed to the shaft 56. The shaft 56 projects laterally outwardly from the lower end of the upright support 55 and is spline connected to the planing or cutting drum 16, to drive the latter.

The lower end of the support 55 has oppositely directed trunnions 62, 63 which are secured in bearings 64, 65, respectively. The bearings 64, 65 are formed on a bale-like connecting arm 66, that eaxtends down around the lower end of the upright support 55, and between the bearings 64, 65. Trunnions 67, 68 are secured to the main frame 11 behind the trunnions 62, 63, and somewhat in alignment with the latter. The inner end of the connecting arm 66, is pivotally secured to the trunnions 67, 68 to provide a movable support for the lower end of the upright support 55 on the main frame 11.

There is a further connection of the upright support 55 to the main frame 11 by a double acting hydraulic lift cylinder 70 and a double-acting hydraulic tilt cylinder 71. The hydraulic lift cylinder 70 has its cylinder end secured to the main frame 11 by a pivot 72 and its rod end is secured to the upright support 55 by a pivot 73. The hydraulic tilt cylinder is secured to the main frame 11 by a pivot 74, and its rod end is secured to the upright support 55 by a pivot 75. By retraction and extension of the hydraulic cylinder the upright support 55 and the cutting drum 16 may be lowered or raised with respect to the road surface for adjusting the depth of cut. During such elevational adjustment of the upright support 55 the lower connecting arm 66 and the hydraulic cylinder 71 function as pivoted links which permit the freedom of adjusting movement. However, as the elevation of the cutting drum 16 is adjusted by the lift cylinder 70 its inclination changes slightly due to the unequal linkage lengths of the connecting arm 66, and the hydraulic cylinder 71. The inclination of the cutting drum 16 can then be adjusted by the hydraulic tilt cylinder 71 to the proper inclination to meet the road surface. Hydraulic fluid for operating the lift cylinder 70 and the tilt cylinder 71 is supplied by the hydraulic pump 53.

The cutting drum is formed with a cylinder 76, and

a plurality of blocks 77 that are secured to the circumference of the cylinder 76, as by welding, and extending radially outwardly therefrom. A cutting bit 78 .is secured in each of the blocks 77, and arranged in a suitable lacing pattern. The cutting bits 78 are subject to wear and therefore, are releasably secured in the blocks 77, to permit these to be changed from time to time.

Referring now to FIG. 4, there is a diagrammatic il lustration of the hydraulic circuit for operating the various elements of the road planing machine 10. The charging pump 24 takes hydraulic fluid from the tank 79 and supplies this to the reversible and variable speed pump 22, which in turn supplies hydraulic fluid to the hydraulic motors 20, 21 for the fore and aft wheels 12, 13, respectively, to drive the latter. There is a relief valve 80 connected across the pump to relieve excess pressure of the hydraulic fluid should this occur. The pump 22 and the motors 20, 21 are in a hydrostatic drive, and the operation of the pump 22 is controlled as to direction and speed to control the operation of the motors 20, 21 accordingly, whereby the direction of travel and the speed of the road planing machine 10 is controlled.

The pump 54 draws hydraulic fluid from the tank 79 and supplies hydraulic fluid to the hydraulic motor 56 for operating the cutting drum 16 as previously described. There is a valve 81 by which the operation of the hydraulic motor 56 may be controlled to start and stop the operation of the motor 56.

The pump 53 also draws hydraulic fluid from the tank 79 and supplies the hydraulic fluid for operation of the steering cylinder 43, the lift cylinder 70 and the tilt cylinder 71. The hydraulic fluid flows from the pump 53 to a flow control valve 82 which directs a preselected quantity of flow of hydraulic fluid to the hydraulic steering control valve 52 by which the flow of hydraulic fluid is controlled to the double acting hydraulic steering cylinder 43 for operating the steering linkages as previously described.

The remaining flow of hydraulic fluid flows from the flow control valve 82 to a second flow control valve 83, which directs a pre-selected quantity of flow of hydraulic fluid to the control valves 84, 85 for the lift cylinder 70 and the tilt cylinder 71, respectively. Each of the control valves 84, 85 is preferably a three position valve, having two positions for controlling the direction of flow of the hydraulic fluid to double acting hydraulic cylinders 70, 71, respectively, for adjusting the upright support 55 and the cutting drum 16, as previously described. The valves 84, 85 each has a neutral centered position in which the flow of hydraulic fluid is blocked to the hydraulic cylinders 70, 71 and the latter are held fixed in their adjusted positions.

Thus, there is provided a road planing machine which is constructed such that it can efficiently operate in close places to remove material from road surfaces in small areas and around obstructions such man-hole covers. The arrangement of the planing or cutting drum in longitudinal alignment with the fore and aft steering wheels and mid-way there between permits the turning of the machine in a small circle, thereby operating the cutting drum in a curved path to make close turns. The supporting wheel on the opposite side of the road planing machine is in transverse alignment with the cutting drum thereby to maintain the accuracy and closeness of the turn in the operation of the cutting drum. The cutting drum may be adjusted to cut the material to a pre-selected depth, and the inclination of the cutting drum may be adjusted to meet the grade of the road surface.

Obviously those skilled in the art may make various changes in the details and arrangement of parts without departing from the spirit and scope of the invention as defined by the claims as hereto appended, and I wish therefore not to be restricted to the precise construction herein disclosed.

Having thus described and shown an embodiment of the invention, what it is desired to serve by Letters Patent of the United States, is:

l. A planing machine for planing roads or other paved surfaces, comprising:

a frame;

first and second ground engaging supporting means mounted at fore and aft locations along one side of said frame;

third ground engaging supporting means mounted on the opposite side of said frame, said first, second and third ground engaging means co-operatively supporting said frame on said surface and capable of moving said frame along a smooth tightly curved path on said surface;

rotary planing means mounted on said frame intermediate and in alignment with said fore and aft ground engaging means and in transverse alignment opposite said third ground engaging means, said planing means being adapted to engage the paved surface for cutting material from the paved surface to a controlled depth; and

power means to propel said machine along said surface and to drive said rotary planing means.

2. A planing machine for planing road surfaces as recited in claim 1 in which each of said ground engaging supporting means includes a rotatably mounted wheel, and said power means includes means to drive said fore and aft wheels.

3. A planing machine for planing road surfaces as recited in claim 2 in which said planing means is disposed midway between said fore and aft ground engaging wheels.

4. A planing machine for planing road surfaces as recited in claim 2 in which said planing means comprises a rotary cutting drum disposed midway between said fore and aft ground engaging wheels, and wherein said power means comprises hydraulic power means to rotate the fore and aft wheels and separate hydraulic power means to rotate said cutting drum in engagement with the road surface.

5. A planing machine for planing road surfaces as recited in claim 3 in which each of said fore and aft wheels is mounted on an upright pivot, and further including a steering linkage connected to each of said fore and aft wheels to turn the wheels on their respective pivots for steering the planing machine and to operate said cutting drum in a curved path, and hydraulic power means to operate said steering linkage.

6. A planing machine for planing road surfaces as recited in claim 2 in which each of said fore and aft ground engaging wheels is mounted on an upright pivot for steering the planing machine and to operate said planing means in a curved path.

7. A planing machine for planing road surfaces as recited in claim 6 in which said planing means comprises a cutting drum disposed on a transverse axis, means to rotate said cutting drum in engagement with the road surface, and the axis of said cutting drum and the axis of said ground engaging wheel of said third supporting means being located in the same upright plane.

8. A planing machine for planing road surfaces as recited in claim 7 in which said cutting drum has radially extending cutting bits secured to said cutting drum in positions effective to engage the road surface and remove material therefrom upon rotation of said cutting drum.

9. A planing machine for planing road surfaces as recited in claim 7 including a support for said planing means on said main frame, said support extending down toward the road surface to support the planing means at the road surface, lift adjusting means to adjust the elevation of the support and the planing means relative to the ground surface, and tilt adjusting means to adjust the inclination of the axis of said planing means relative to the ground surface.

10. A planing machine for planing road surfaces as recited in claim 9 including means to connect said lift adjusting means between said main frame and said support, and means to connect said tilt adjusting means between said main frame and said support.

11. A planing machine for planing road surfaces as recited in claim 9 including pivoted connecting means for said support on said main frame to permit elevating movement and tilting movement of the support relative to said main frame.

12. A planing machine for planing road surfaces as recited in claim 9 including a connecting link between said support and said main frame, first pivot means to hold said connecting link to said main frame and second pivot means to hold said connecting link to said support to permit elevating movement and tilting movement of the support relative to said main frame by movement of said support and said connecting link about said first and second pivot means.

13. A planing machine for planing road surfaces as recited in claim 12 in which said lift adjusting means comprises an extensible and retractable hydraulic cylinder, pivot means connecting the ends of said lift hydraulic cylinder to said main frame and to said support, respectively, said tilt adjusting means comprises an extensible and retractable hydraulic cylinder, and pivot means connecting the ends of said tilt hydraulic cylinder to said main frame and to said support, respectively.

14. A planing machine for planing road surfaces comprising, a longitudinally extending main frame, ground engaging supporting means to support the planing machine on a road surface, said ground engaging supporting means including a fore ground engaging wheel and an aft ground engaging wheel mounted on one side of the main frame and a ground engaging wheel at the opposite side of the main frame, planing means adapted to engage the road surface for cutting material from the road surface to a pre-selected depth, means for turning the fore and aft wheels to steer the planing machine, and the axes of said fore and aft wheels and the axis of said opposite wheel intersecting each other in a point in all turned positions of said fore and aft wheels for all the wheels to travel in arcuate paths about said point of intersection as a center.

15. A planing machine for planing road surfaces as recited in claim 14 in which said fore and aft ground engaging wheels are disposed at approximately opposite ends of said main frame, and said opposite ground engaging wheel is disposed intermediate said fore and aft wheels in the longitudinal direction of the main frame.

16. A planing machine for planing road surfaces as recited in claim 15 in which said planing means comprises a rotary drum on a transversely extending axis and disposed to operate in an arcuate path about said point of intersection in all turned positions of said fore and aft wheels.

17. A planing machine for planing road surfaces as recited in claim 14 in which said opposite ground engaging wheel is disposed midway between said fore and aft wheels in the longitudinal direction of said main frame, and the turning movement of said fore and aft wheels is equal.

18. A planing machine for planing road surfaces as recited in claim 17 in which each of the fore and aft wheels is mounted on an upright pivot, and steering linkage means to turn said fore and aft wheels in opposite directions about the axis of each upright pivot, re-

spectively.

19. A planing machine for planing road surfaces as recited in claim 14 in which said planing means is disposed in longitudinal alignment with said fore and aft wheels and midway between said fore and aft wheels, and said planing means is disposed in transverse alignment with said opposite wheel.

20. A planing machine for planing road surfaces as recited in claim 19 in which said planing means comprises a rotatable drum with radially directed road surface engaging bits, said planing means drum being disposed on a transverse axis that is in an upright plane with the axis of said opposite wheel. 

1. A planing machine for planing roads or other paved surfaces, comprising: a frame; first and second ground engaging supporting means mounted at fore and aft locations along one side of said frame; third ground engaging supporting means mounted on the opposite side of said frame, said first, second and third ground engaging means co-operatively supporting said frame on said surface and capable of moving said frame along a smooth tightly curved path on said surface; rotary planing means mounted on said frame intermediate and in alignment with said fore and aft ground engaging means and in transverse alignment opposite said third ground engaging means, said planing means being adapted to engage the paved surface for cutting material from the paved surface to a controlled depth; and power means to propel said machine along said surface and to drive said rotary planing means.
 2. A planing machine for planing road surfaces as recited in claim 1 in which each of said ground engaging supporting means includes a rotatably mounted wheel, and said power means includes means to drive said fore and aft wheels.
 3. A planing machine for planing road surfaces as recited in claim 2 in which said planing means is disposed midway between said fore and aft ground engaging wheels.
 4. A planing machine for planing road surfaces as recited in claim 2 in which said planing means comprises a rotary cutting drum disposed midway between said fore and aft ground engaging wheels, and wherein said power means comprises hydraulic power means to rotate the fore and aft wheels and separate hydraulic power means to rotate said cutting drum in engagement with the road surface.
 5. A planing machine for planing road surfaces as recited in claim 3 in which each of said fore and aft wheels is mounted on an upright pivot, and further including a steering linkage connected to each of said fore and aft wheels to turn the wheels on their respective pivots for steering the planing machine and to operate said cutting drum in a curved path, and hydraulic power means to operate said steering linkage.
 6. A planing machine for planing road surfaces as recited in claim 2 in which each of said fore and aft ground engaging wheels is mounted on an upright pivot for steering the planing machine and to operate said planing means in a curved path.
 7. A planing machine for planing road surfaces as recited in claim 6 in which said planing means comprises a cutting drum disposed on a transverse axis, means to rotate said cutting drum in engagement with the road surface, and the axis of said cutting drum and the axis of said ground engaging wheel of said third supporting means being located in the same upright plane.
 8. A planing machine for planing road surfaces as recited in claim 7 in which said cutting drum has radially extending cutting bits secured to said cutting drum in positions effective to engage the road surface and remove material therefrom upon rotation of said cutting drum.
 9. A planing machine for planing road surfaces as recited in claim 7 including a support for said planing means on said main frame, said support extending down toward the road surface to support the planing means at the road surface, lift adjusting means to adjust the elevation of the support and the planing means relative to the ground surface, and tilt adjusting means to adjust the inclination of the axis of said planing means relative to the ground surface.
 10. A planing machine for planing road surfaces as recited in claim 9 including means to connect said lift adjusting means between said main frame and said support, and means to connect said tilt adjusting means between said main frame and said support.
 11. A planing machine for planing road surfaces as recited in claim 9 including pivoted connecting means for said support on said main frame to permit elevating movement and tilting movement of the support relative to said main frame.
 12. A planing machine for planing road surfaces as recited in claim 9 including a connecting link between said support and said main frame, first pivot means to hold said connecting link to said main frame and second pivot means to hold said connecting link to said support to permit elevating movement and tilting movement of the support relative to said main frame by movement of said support and said connecting link about said first and second pivot means.
 13. A planing machine for planing road surfaces as recited in claim 12 in which said lift adjusting means comprises an extensible and retractable hydraulic cylinder, pivot means connecting the ends of said lift hydraulic cylinder to said main frame and to said support, respectively, said tilt adjusting means comprises an extensible and retractable hydraulic cylinder, and pivot means connecting the ends of said tilt hydraulic cylinder to said main frame and to said support, respectively.
 14. A planing machine for planing road surfaces comprising, a longitudinally extending main frame, ground engaging supporting means to support the planing machine on a road surface, said ground engaging supporting means including a fore ground engaging wheel and an aft ground engaging wheel mounted on one side of the main frame and a ground engaging wheel at the opposite side of the main frame, planing means adapted to engage the road surface for cutting material from the road surface to a pre-selected depth, means for turning the fore and aft wheels to steer the planing machine, and the axes of said fore and aft wheels and the axis of said opposite wheel intersecting each other in a point in all turned positions of said fore and aft wheels for all the wheels to travel in arcuate paths about said point of intersection as a center.
 15. A planing machine for planing road surfaces as recited in claim 14 in which said fore and aft ground engaging wheels are disposed at approximately opposite ends of said main frame, and said opposite ground engaging wheel is disposed intermediate said fore and aft wheels in the longitudinal direction of the main frame.
 16. A planing machine for planing road surfaces as recited in claim 15 in which said planing means comprises a rotary drum on a transversely extending axis and disposed to operate in an arcuate path about said point of intersection in all turned positions of said fore and aft wheels.
 17. A planing machine for planing road surfaces as recited in claim 14 in which said opposite ground engaging wheel is disposed midway between said fore and aft wheels in the longitudinal direction of said main frame, and the turning movement of said fore and aft wheels is equal.
 18. A planing machine for planing road surfaces as recited in claim 17 in which each of the fore and aft wheels is mounted on an upright pivot, and steering linkage means to turn said fore and aft wheels in opposite directions about the axis of each upright pivot, respectively.
 19. A planing machine for planing road surfaces as recited in claim 14 in which said planing means is disposed in longitudinal alignment with said fore and aft wheels and midway between said fore and aft wheels, and said planing means is disposed in transverse alignment with said opposite wheel.
 20. A planing machine for planing road surfaces as recited in claim 19 in which said planing means comprises a rotatable drum with radially directed road surface engaging bits, said planing means drum being disposed on a transverse axis that is in an upright plane with the axis of said opposite wheel. 